The objective of this project is to attempt to gain insight into the mechanisms regulating globin gene expression in development. In particular, we have been interested in studying how position effects and gene dosage may affect the expression of globin genes. To carry out such studies, we generated a number of mice that are stably transformed with exogenously introduced mouse b-major globin genes. The transformants were obtained by microinjecting the cloned b-major globin gene into fertilized eggs and then surgically transferring the eggs back into a foster mother for development to term. We have four such strains of animal: one with 1 copy, one with 6 to 9 copies, one with 150 copies, and one with over 1,000 copies of the injected globin gene. We have analyzed the integration events by restriction analysis and in situ chromosome hybridization. We have analyzed the blood and the hemoglobins of these animals to determine if there is any sign of anemia or thalassemia. Currently, we are analyzing the RNA transcripts of these animals to determine if there is transcription from the exogenous globin genes, and whether such transcription exhibits any tissue specificity. (M)